Implantable medical devices (IMD) such as cardiac and neural stimulators utilize circuitry within an enclosure to generate electrical stimulation pulses. The circuitry is electrically linked to contacts within a header that is attached to the enclosure by a set of conductive pins known as a feedthrough. The implantable medical leads are physically connected to the header and include connectors on a proximal end that engage the electrical connectors within the header. The implantable medical leads also include electrodes near a distal end with the conductors carrying the stimulation pulses from the connectors to the electrodes.
The number of leads needed for a particular therapy and corresponding IMD may vary as may the number of electrical connections per lead. Hence the design of the header must also vary to accommodate the feedthrough of a given device and the number of leads and lead connectors that are necessary. For example, 24 electrodes may be configured in numerous ways for a device and therapy. One neurostimulator may drive eight electrodes per lead for three leads. Another neurostimulator may drive eight electrodes per lead for two leads and four electrodes per lead for two additional leads. Yet another neurostimulator may drive twelve electrodes per lead for two leads.
In these variations, entirely different header designs are used. Such header designs conventionally use ribbon bonds and lead frames as the interconnection between the feedthrough and the pressure contact, often a canted-coil spring, in the header. The development and resulting design for the ribbon bonds, lead frames, and related feedthrough become very specific for each IMD model and related leads and do not directly transfer to other IMD models and leads. Furthermore, the manufacturing processes to construct the headers having distinct designs for the different IMD models can be challenging. Thus, the development and manufacturing processes for headers being designed for each of the IMD models is burdensome.
In addition to the burdens of development and manufacturing, the designs that involve a relatively large number of pressure contacts in the header per lead can be troublesome. Typically, the pressure contacts such as the canted-coil springs can necessitate a large insertion force when numerous pressure contacts are needed for a particular lead. The insertion force may exceed the capabilities of the lead to maintain physical integrity. Lead insertion may be difficult and lead damage may also occur during insertion.
Additionally, because the header is rigidly attached to the IMD enclosure, the insertion of each lead requires some degree of manipulation of the IMD to correctly align the lead with the lead passageway of the header. This becomes progressively more burdensome as leads are sequentially inserted and begin to crowd and clutter the area immediately adjacent the entryway to the header.
Furthermore, the size of the header is directly related to the connector spacing on the lead, or lead pitch. As the number of electrodes per lead increases the header size increases, and the increase may be significant due to the relatively large size of conventional electrical contacts such as the canted-coil springs. This relationship contradicts the efforts to develop smaller IMDs which are often more desirable for implantation.